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What contaminants
may be found in drinking water?
There is no such thing as naturally pure
water. In nature, all water contains some impurities. As water flows
in streams, sits in lakes, and filters through layers of soil and rock
in the ground, it dissolves or absorbs the substances that it touches.
Some of these substances are harmless. In fact, some people prefer mineral
water precisely because minerals give it an appealing taste. However,
at certain levels minerals, just like man-made chemicals, are considered
contaminants that can make water unpalatable or even unsafe.
Some contaminants come from erosion of
natural rock formations. Other contaminants are substances discharged
from factories, applied to farmlands, or used by consumers in their homes
and yards. Sources of contaminants might be in your neighborhood or might
be many miles away. Your local water quality report tells which contaminants
are in your drinking water, the levels at which they were found, and the
actual or likely source of each contaminant.
Some ground water systems have established
wellhead protection programs to prevent substances from contaminating
their wells. Similarly, some surface water systems protect the watershed
around their reservoir to prevent contamination. Right now, states and
water suppliers are working systematically to assess every source of drinking
water and to identify potential sources of contaminants. This process
will help communities to protect their drinking water supplies from contamination,
and a summary of the results will be in future water quality reports.
For more information
- Read a list of the
drinking water contaminants that EPA regulates , including their sources
in drinking water and their potential health effects.
- How does arsenic get in drinking water? How do people use vinyl chloride? a set of fact sheets provides information
on each contaminant that EPA regulates, including its tradename(s),
areas in which it is commonly found, its possible health effects, etc.
- Non-point source pollution, such as runoff from farmlands and urban
stormwater, is one of the greatest threats to water quality today. To
learn more about this threat, see EPA's Non-point
source pollution site.
- To learn about the source water assessment process in your state, visit
EPA's local drinking
water information web site, which will help you find the state's web
site and source water protection coordinator.
- To find information about locations where there are substances present
that may contaminate sources of drinking water (for example, Superfund
sites), visit EPA's Envirofacts web site, where you can search by your location, zip code, etc. You can
also use the
Enviromapper function to plot the information that you find on a map.
Return to Drinking
Water & Health: what you need to know
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